1. Field of the Invention
The present invention relates to an external, battery powered therapeutic electrical stimulator, and more particularly to a quick change battery drawer for rapidly substituting a fresh battery for an exhausted battery while the stimulator continues to emit electrical stimulation to treat a patient.
2. Description of the Background Art
External, battery powered electrical stimulators, e.g. cardiac pacemakers and neurological stimulators, are widely used in the treatment of patients while the patients are ambulatory or confined in a medical facility. Portable, battery powered cardiac pacemakers may be strapped to a patient to provide a degree of freedom of movement even when the patient is confined and are used by ambulatory patients recovering from open heart surgery or otherwise requiring temporary pacing.
With external pacemakers typically used during a patient stay in a medical facility, the appropriate temporary lead system may be implanted in the patient, depending on the patient need, and the pulse generator may be switched to operate in one of the pacing modes prescribed by the attending physician. For example, during open heart surgery, temporary atrial and ventricular electrode beating leads may be implanted in the heart for post-operative dual chamber pacing during the recovery period and until the leads are removed. If one of the electrodes is dislodged from the heart, it may be necessary to switch to the appropriate single chamber pacing mode for the remaining electrode. In other cases, temporary single chamber pacing may be prescribed from the outset. Such typical external pacemaker pulse generators include the Medtronic.RTM. Model Nos. 5342, 5345 and 5346 external pacemakers, the Telectronics.RTM. Model 4553 external pacemaker, and the Pacesetter Systems, Inc. Model 3070 external pacemaker.
Such patients may be entirely or intermittently dependent on the temporary pacing therapy being delivered. After a period of pacing, it becomes necessary to replace the battery powering the pulse generator because the battery energy depletes. It is then necessary to quickly change the battery or substitute another pulse generator for the pulse generator being used. For patient's whose hearts are dependent on the continuous application of the pacing therapy, the loss of pacing during the replacement time may develop symptoms that are upsetting to the patient and the staff member making the battery change.
In the above-referenced Medtronic.RTM. external pacemaker pulse generators, the power supply circuit includes a capacitor for storing energy sufficient to maintain pacing for a brief period if the battery is removed. The electrical connection of the battery to the power supply circuit is maintained by contacts that are closed when the battery drawer is fully latched and opened as the drawer latch is released and the drawer is initially moved.
Full removal of the battery is effected by unlatching the battery drawer, manually pulling the drawer fully out of the drawer opening and retrieving the battery from the drawer. Due to manufacturing tolerances and aging of the plastic housing, the drawer sides and bottom may bind with the sides and bottom of the drawer opening into the housing, making it difficult to pull out the drawer, thereby increasing the replacement time.